The Technology Behind Positive Displacement Blowers

Aerzen has been developing positive displacement blowers based on the Roots principle since 1868. Later, in 1987, the company launched the three-lobe blower in the market, while patenting the process technology at the same time. Building on these many years of experience, the company has developed the positive displacement blower into a sophisticated high-tech product.

Functionality of the Positive Displacement Blower

The conveying direction is related to both the installation position of the stage and the turning direction of the rotors. Based on the assumption that the standard installation position offers vertical conveyance, and that the rotational direction makes the top-to-bottom conveyance simple, the fundamental principle is as follows: as shown, the air flows from the upper inlet port into the stage.

In tandem with the lobes and the exterior wall of the pistons, the rotors’ revolutions create so-called “conveying chambers”, where ambient pressure is still present. Once the first lobe passes the opening to the pressure side, the system pressure is altered. This is referred to as isochoric compression. The rotors seal off each other to the inside, preventing a change of pressure.

Technology

Compression Principle

The positive displacement blowers are operated using the isochoric compression principle, also known as external compression. The pressure increase is achieved by intermittently transporting a gaseous medium, for example, atmospheric air, into a system. The associated increase in pressure is achieved by forcing the medium from atmospheric conditions into a system with a specified resistance, for instance, a water column. In order to overcome this resistance, the blower must operate at a specific output level. Aerzen calls this “coupling performance” (Pk).

Delta Blowers

Versatility in Numbers

Delta Blowers are solid all-rounders— the smallest packaged units are mounted to silo trucks, and the largest machines are employed to operate lifting systems. Delta Blowers can be used to unload transport ships, and demonstrate an hourly performance of up to 1,000 tons.

p1: Pressure at the blower inlet
p2: Pressure at the blower outlet
pV: Suction and pressure loss taking place at the inlet and outlet (also dependent on periphery)
∆p: Difference between intake and discharge pressure

The horizontal axis represents the “volume flow” Q

Q0: Theoretical volume flow which is defined by the volume in the conveying chamber in the blower
QV: Volume flow loss which is produced by the medium flowing back in the clearances of the conveying chamber (between rotor lobe and housing)
Q1: Usable volume flow

The resulting areas correspond to the power requirement. Technically, this can be inferred mathematically from the following formula:

P = Q* ∆p

The following can be inferred from the main formula.

Pth: The theoretical power requirement Pth is determined by multiplying the differential pressure ∆p with the theoretical volume flow Q0.

Pth =Q0 *∆p

In the above illustration, the power requirement corresponds to the area a-b-c-d.

PK: For the theoretical power requirement Pth, performance losses PV is also considered by the coupling performance PK.

PK=Pth+ PV=Q0 *(∆p+pV)

In the above example, coupling performance corresponds to the area a-b-e-f.

Characteristics of the Positive Displacement Blower

Presently, positive displacement blowersof the Delta Blower Generation 5 act as the driving force behind a number of processes, and are the central part of a robust machine combination.

Aerzen has introduced a variety of innovations with this new series, and these developments represent exceptional blower power for oil-free conveyance of air and neutral gases, without the need for absorbing media. Positive displacement blowers offer a large volume of flow range from 30 to 15,000 m3/hour with lowered life-cycle costs, easier handling, and even quieter operation.

However, one thing has not changed: the blower class continues to be highly reliable, tremendously robust, and has an exceptionally long service life. Therefore, it is unsurprising that customers select these blowers for continuous, long-term applications over years and decades.

This information has been sourced, reviewed and adapted from materials provided by Aerzener Maschinenfabrik GmbH.